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I am testing a solution for a tax calculation system, and some states have zip code ranges with specific taxes, so I need to know if there are zip codes that correspond to different locations. One part of the system uses different combinations of city/zip to find the county, because some locales have taxes that vary by county.

Are there zip codes that correspond to more than one location but are separate from each other, possibly in different states or counties?

I know that a zip code can span cities and/or states but I want to know if there are zip codes that are completely autonomous of one another but share the same code.

Is there a way that I can find up-to-date information about this?

Malachi
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  • Please define "duplicate". Are you asking if two different cities can have the same zip code? Perhaps you want to know if one area can be called two different things, but have the same zip code? Are you asking if one zip code can be in two different counties? Are you asking if you can have the same zip code in a different state? Are you asking if one geographic area (say a certain building) can have two different codes? How "duplicate" do you mean? Have you Googled or read Wikipedia to better understand a Zip Code? – Keeta - reinstate Monica May 08 '18 at 18:31
  • @Keeta, I apologize for being ambiguous with my question, I know that a zip code can span cities and/or states but I wanted to know if there are zip codes that are completely autonomous of one another but share the same code. – Malachi May 08 '18 at 18:35
  • Suggest relating...I think this question would have been answered by reading the detailed answer in: https://gis.stackexchange.com/questions/53918/determining-which-us-zipcodes-map-to-more-than-one-state-or-more-than-one-city – Keeta - reinstate Monica May 08 '18 at 18:42
  • I actually read that thread, and didn't find the answer that I was looking for, @Keeta – Malachi May 08 '18 at 18:44

3 Answers3

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There are no duplicate ZIP Codes. There are some ZIP Codes that are multi-part polygons, but those polygons are usually adjacent.

Source: I manage/update ZIP Codes for the USPS

Maksim
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    In Pennsylvania, the Post office boundaries do not align with the township boundaries, like Saylorsburg PA, is part of Ross Twp, Hamilton twp, and Chestnuthill Twp, so the taxing and PO do not align. You also had multiple township using the same Post Office Like Clifton Twp, Covington Twp, and Thornhurst all using the same zip code as Gouldsboro, PA. I worked with the townships and Post Office on 911 addressing for this. – Bill Chappell May 08 '18 at 17:55
  • Looking at the authoritative data, there are 39084 ZIP Code boundaries – Maksim May 08 '18 at 18:00
  • you said, usually adjacent, what about when they are not adjacent? – Malachi May 08 '18 at 18:10
  • Then they are across the road from each other typically, very close – Maksim May 08 '18 at 18:13
  • there can be multiple cities/twp in a zip code, but not the same zip code in two separated places. that is what you mean by There are some ZIP Codes that are multi-part polygons, but those polygons are usually adjacent. correct? – Malachi May 08 '18 at 18:25
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    That is correct – Maksim May 08 '18 at 18:26
  • So in which case I think this says there is no case of get canonical zip code for address can return more than one value. – Joshua May 08 '18 at 21:06
  • In Germany, there are cities having multiple ZIP codes (e.g. Hamburg). Is this also the case in the US? – Sebastian Mach May 09 '18 at 08:26
  • @SebastianMach, yes, there are cities that have multiple ZIP codes. a lot of them do. – Malachi May 09 '18 at 11:42
  • @Malachi & Maxim... sometimes the codes are actually discontinuous, separated entirely by address ranges in another ZIP. Sometimes it's only by a little like the weirdness around 72367 and 72328 in Arkansas, but sometimes it's by over a mile like 72355 in Lexa AR or the neat three-parter 49886 in Spalding MI. – Zack May 02 '23 at 03:46
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There ARE duplicate zip codes in the USA.

Look up zip code 34993, or 34934 along with many others that are the same zip code in 2 different states.

34993 is in Florida and Arkansas

you can look up the others.

Tom
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The City of Florence, KY, USA & Fiorano Modenese, Modena, Italy, and Dong-gu, Daegu, South Korea have the same zip code of 41042

Casey Caddell
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    Thank you for taking the time to read my question, but I was looking in the United States of America specifically. Your Answer, while related, isn't helpful in answering my question. – Malachi Mar 17 '21 at 15:57